Current leakage relates to characteristic deterioration in reliability, service life, and high-voltage operation of a device, thus it is important to manufacture a reliable device based on group III nitride light-emitting diodes.
It has been known that a group III nitride light-emitting device has bad electrostatic characteristics in comparison with light-emitting devices made of other compounds. As an example, crystal defects, which is occurred on the group III nitride semiconductor layer grown on a substrate due to a lattice mismatch between the substrate and the group III nitride semiconductor layer, spread to a growth direction of the group III nitride semiconductor layer, thereby forming a threading dislocation.
The crystal defects increase current leakage of device, and in the case of introducing an external static electricity, an active layer of the light-emitting device having many of crystal defects is broken by a strong field. Generally, it is known that crystal defects (threading dislocation) of 109 to 1011/cm2 exist on a GaN thin film.
The electrostatic destruction characteristics of the light-emitting device are very important issues related to an application range of GaN-based light-emitting devices.
Particularly, a design of device for withstanding static electricity generated from package devices and workers of the light-emitting device is very important parameter for improving the yield of a final device.
Particularly, electrostatic characteristics have become more important since the GaN-based light-emitting device is recently applied to and used in bad condition environments such as outdoor signboards, vehicle lights, etc.
Generally, an ESD of a conventional GaN light-emitting device withstands several thousand volts in a forward direction under Human Body Mode (HBM), whereas it does not withstand several hundred volts in a reverse direction. As described above, the main reason is the crystal defects of the device, and also, an electrode design of the device is very important. In particular, since a sapphire substrate is generally used in GaN light-emitting device as an insulator, the ESD characteristics are further deteriorated by intensifying a concentration phenomenon of currents around an N-electrode during a practical device operation as the N-electrode and a P-electrode are formed at the same plane on the structure of the device.
Various methods configured to improve characteristics of light-emitting device and other electronic devices by reducing density of threading dislocation defect are proposed in the related art as follows.
For instance, in Korean Patent No. 10-1164026 (registration date: 2012 Jul. 18), Korean Patent Application Publication No. 10-2013-0061981 (publication date: 2013 Jun. 12), and Korean Patent Application Publication No. 10-2014-0145368 (publication date: 2014 Dec. 23) a growth method was introduced, wherein a Hexagonal v-pit (V-shaped pit) was formed on each of threading dislocations, and when v-pits were formed on an active layer, the active layer was formed thinly on a sidewall and had high band gap so that a barrier height was increased and non-radiative recombination was minimized, therefore, an internal quantum efficiency is increased. However, the conventional techniques have a problem with reduced optical output due to a decrease in an overall light-emitting region, since the v-pit area of the active layer was excluded from a light-emitting region in such a structure.